To determine the incidence and "structure" of augmented breaths (AB) in neonates, we studied 13 preterm infants (GA 31± 0.4 wk; BW 1.56±0.09 kg; PNA 25±4 days) and 11 term infants (GA 40±0.3 wk; BW 3.4±0.14 kg; PNA 4±0,8 days). The incidence of AB was higher in periodic than in regular breathing both in preterm (0.914±0.07 vs 0.434±0.09 breaths/min; p=0.0063) and in term infants (0.803±0.09 vs 0.406±0.04 breaths/min; p=0.0009). In term infants the incidence was greater in active than in quiet sleep (0.79±0.12 vs 0.48±0.06 breaths/min; p=0.02). VT of the AB was 18.9±0.71 ml as compared to 7.5±0.71 (p<0.001) during control in quiet sleep in preterm infants. The increased VT was associated with an increase in Ti from 0.46±0.03 to 0.80±0.04 seconds (p<0.001), in VT/Ti from 15.9±1.46 to 23.5±1.8 ml/sec (p<0.001) with no change in Ttot. Instantaneous ventilation increased from 0.327±0.041 to 0.666±0.073 L/min/kg (p<0.001). VT of the first inspiratory component of the AB was greater than VT of control breaths, but similar changes in VT in other control periods was not associated with AB. Airway occlusion produced no pressure-on-the-top-of-a-pressure pattern but was followed by AB after occlusion was released. Results suggest, 1) ABs are highly correlated with prematurity, periodic breathing and active sleep; 2) their appearance is not dependent on chemical drive or volume alone. We speculate that both chemical drive and lung volume changes are important to induce augmented breaths in neonates.
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Clinics in Perinatology (1992)